Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
Not for profit educational resource on indoor environmental quality.
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Fundamentals of indoor environmental quality / thermal comfort and air quality solutions using radiant based HVAC

One of the myths perpetuated with radiant cooling systems is condensation risk on the cooling surface. This would be a real risk if there was no moisture control. Without moisture control numerous risk factors develop such as hydrolysis.  From Princeton University, "Hydrolysis is a chemical reaction during which molecules of water (H2O) are split into hydrogen cations (H+, conventionally referred to as protons) and hydroxide anions (OH−) in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers...".

Clearly you can see in Figure 1 that in this specific study by Dr. Richard L. Corsi, paint emissions (specifically HC-O-O) are affected by rising relative humidity.[1]  Matthews et al. noted that changing the indoor conditions from
68F (20C) and 30% relative humidity (RH) to 79F (26C) and 60% RH would result in two to fourfold increases in formaldehyde concentration for the same air change rate.[2] Hodgson et al stated in their study on the topic, "This suggests that indoor humidity has a substantial impact on formaldehyde emission rates and concentrations." [2]

There is an exhaustive supply of research addressing this topic and readers are encouraged to seek out these documents for detailed study. For our purposes here, it is enough to say once again moisture must be controlled in habitable spaces which ultimately enables the successful use of radiant cooling. 

This content is a key component from our course, "Integrated HVAC Engineering: Mastering Comfort, Health, and Efficiency."


1. Relative humidity and paint emissions (HC-O-O) adapted Richard L. Corsi, Ph.D., PE , Building Energy & Reactivity Complex Interactions.  Simple Solutions, IAQ 2013 – Environmental Health in Low Energy Buildings – Vancouver, BC, Canada October 17th, 2013
2. Hodgson, Alfred T., Steven J. Nabinger, and Andrew K. Persily. 2004. “Volatile Organic Compound Concentrations and Emission Rates Measured over One Year in a New Manufactured House.” doi:10.2172/838617.


See also:

Radiant Cooling - Part I, Fundamentals
Radiant Cooling Systems: Calculation Example
Tres Bien for Large Scale Radiant Cooling
Radiant Cooling for Sceptics: How to do radiant cooling in high humidity geographies
Radiant based HVAC systems - bibliography / resources
Radiant Cooling Systems: Condensation Concerns Part 1 of 6, Preservation of Materials
Radiant Cooling Systems: Condensation Concerns Part 2 of 6, Microbial
Radiant Cooling Systems: Condensation Concerns Part 3 of 6, Hydrolysis
Radiant Cooling Systems: Condensation Concerns Part 4 of 6, Dimensional Stability of Hygroscopic Materials
Radiant Cooling Systems: Condensation Concerns Part 5 of 6, Respiratory Discomfort
Radiant Cooling Systems: Condensation Concerns Part 6 of 6, Thermal Comfort



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